The emergence of quantum computers poses a significant risk to Bitcoin's security, with the potential to compromise the cryptocurrency's core cryptography. According to recent research by Google, a sufficiently powerful quantum computer could crack Bitcoin's core cryptography in under nine minutes, which is faster than the average time it takes for a Bitcoin block to be settled.
This has sparked concerns among developers, who are now considering various upgrades to build defenses against this potential threat. Approximately 6.5 million bitcoin tokens, worth hundreds of billions of dollars, are currently sitting in addresses that could be directly targeted by a quantum computer.
This includes coins belonging to Bitcoin's pseudonymous creator, Satoshi Nakamoto. The potential compromise of these coins would not only result in significant financial losses but also undermine Bitcoin's core principles of 'trust the code' and 'sound money.' To mitigate this threat, several proposals are being considered, including the removal of public keys from the blockchain, the implementation of post-quantum signature schemes such as SPHINCS+, and the introduction of emergency brakes for the mempool. One proposal, BIP 360, suggests removing the public key permanently embedded on-chain, while another proposal, Tadge Dryja's Commit/reveal scheme, aims to protect transactions in the mempool from future quantum attacks.
Additionally, the Hourglass V2 proposal seeks to slow the spending of old coins held in already-exposed addresses, limiting sales to one bitcoin per block to prevent a catastrophic overnight mass liquidation. These proposals are still in the development stage, and their implementation will likely take time due to Bitcoin's decentralized governance structure. Nevertheless, the fact that developers are actively working on solutions to address the quantum computing threat may help alleviate market concerns.